A technology called “deduplication” for not storing duplicated copies of repeating data in a storage apparatus and using the storage area of the storage apparatus more efficiently is known as one of storage system technologies. When it comes to deduplication technology, generally two methods are known: inline and postprocess. With inline deduplication, data for which a write request has been issued is deduplicated and then stored in a storage apparatus before returning a response to the write request. Postprocess deduplication temporarily stores data requested to be written in a storage apparatus in its entirety and then returns a response, and deduplicates the stored data at a later time.
In addition, consideration has been given to employing both inline deduplication and postprocess deduplication together. There is provided, for example, a storage system that performs file-level inline deduplication under a predetermined condition and performs chunk-level postprocess deduplication on files from which duplicates have not been eliminated by the inline deduplication. There is also a proposed technique where a host computer issues a sequential access instruction to a disk storage apparatus.
International Publication Pamphlet No. WO 2013/157103
Japanese Laid-open Patent Publication No. 2000-195147
Postprocess deduplication has a shorter response time to a write request compared to inline deduplication because the deduplication process takes place at a later time. On the other hand, with postprocess deduplication, processing load imposed by the asynchronous and deferred deduplication process may impact the performance of response processing to write requests. Therefore, there remains the problem of how to use the inline and postprocess methods differently to shorten the response time while preventing an increase in processing load.
It is sometimes the case that, for example, a plurality of write requests are sequentially transmitted from the same source. In such a case, the processing efficiency on the source side is improved by shortening the overall response time to the sequential write requests. However, there is the challenge of determining whether to employ inline deduplication for which write requests and postprocess deduplication for which write requests in order to reduce the processing load on an apparatus receiving the write requests as much as possible while shortening the overall response time.